Question

X+y=10 and xy = 21, find 2( x^{​​​​​​2 _{+ Y} 2)}

Answer 1

x+y=10

xy=21 find 2(x^2+y^2)

using the identity

(x+y)^2 = x^2 +y^2+2xy

putting the values
(10)^2=x2+y2+2*21

100=x^2+y^2+42

x^2+y^2=100-42=58

2(x^2+y^2)=2×58=116